Still hot….

Assuming you have Nick's harness already, has the water pump ever been replaced?

 

No you want the tstat to operate the car at the right temp. I wonder if the recore was done right? I know I don't live in Huston but the aging fleet in general just does not see these problems. The system has just a few pieces and they just are not that hard to diagnose for proper operation.

 

Have you replaced the fans?

 

Sounds like you have all of the usual bases covered. I am having my leaking water pump changed too as we speak. 2003 GTA, Part Number 183760/A WATER PUMP-N



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If you end up deciding to go the new radiator route, you might check with the guys that make the aftermarket 512TR radiators, I had emailed with them a couple years back about the 512TR and asked if they also made a 550 radiator and they said send them mine and they'll add it. Still haven't ordered the 512TR radiators or dealt with the 550, but on both cars I am thinking I will just bite the bullet, replace the fuse board, connectors as needed, radiator(s), and fans. And do Nick's harness on the 550 (already in hand).

 

Not sure if this helps, or even if you are having the same issue, but after a Major Service a number of years ago my car ran hot for a few months and A/C kept blowing a fuse. Dealer took many visits to finally find the problem. In the end it looked like some debris from the radiator hose got stuck in the small pump next to the passeger side front wheel. This is what I posted back than after they fixed it.

The Water Re-circulation Pump was replaced. All is well, the AC now works again and the engine temp is back to normal. Of course the dealer states that it had nothing to do with the Major Service just a coincidence. Don't care anymore, after 6 weeks I am just happy to have her back. If this happens to anybody in the future it really is just a small pump behind the passenger front wheel. Probably an hour or two to replace. The dealer charged me for 5 probably because of the diagnoses.

 

"small pump next to the passeger side front wheel."

What pump?

 

Auxiliary water pump, circulates thru the heater core at low power settings. On the (LHD) 456 is behind the right wheel panel. Part number 13.

 

I don't think 550's have that. I have never seen one anyway.

"heater core at low power settings." That's a new one. I have no clue why such a thing would be needed. The WP should provide all the velocity needed even at idle

 

550s have them too. Perhaps that was a bad text description. But it's an electric pump for heater core circulation. 348s use the same (or nearly so) part. Mine gave out Internally a few years ago so I got intimately familiar with them and the German equivalent parts.
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Yeah but that has zero effect on if your car is overheating. That is just bleeding off hot coolant to run heater core. That does not pump coolant to cool fluid like WP pumps water through radiator

 

I have been told by more than one very good radiator shop they would not recore a 550 radiator because no commercially available core had the cooling capacity of the OE. 550 got away with such a small radiator due to the tube design having a very high surface area to volume ratio.

Have you tested for the presence of HC in the coolant?

 

Hydrocarbons. ..it will show if the head gasket is leaking into coolant passages

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Check the radiator cap too. They are real POS and if don't hold pressure mess with cooling. You can order 3 new ones and maybe 1 will work.

 

You guys have always said this. Short of having a way to pressure test the cap, would not seeing evidence of it overflowing or escaping indicate a good cap? What should it hold pressure to?

 

Well if it has the little hose on top then pressure bleeds off there and you never see evidence of it. Sometimes it will bleed water and pressure and you see that in a lower reservoir height. Pressure is in the WSM and or on the cap. WAG It's like 1.3 bar.

And get a heat gun or temp probe in the coolant to see if the ferrari gauge is close to accurate. I never trust ferrari electronics

 

Oh I do love my heat gun. And shooting the reservoir, main hoses, even the radiator itself has been consistent temps and in comparison to the gauge

I have never seen any change in reservoir level nor any coolant residue or droplets from the cap outlet or drain tube